Multiple tank fuel system with emergency pump to maintain required discharge pressure



Jan. 25, 1949. E. M. GAVIN ETAL 2,459,807

MULTIPLE TANK FUEL SYSTEM WITH EMERGENCY PUMP TO MAINTAIN REQUIREDDISCHARGE PRESSURE Filed March 16, 1944 IN VENTORS Eon/4gp M GAVINPatented Jan. 25, 1949 r MULTIPLE TANK FUEL SYSTEM WITH EMERGENCY PUMPTO MAINTAIN RE- QUIRED DISCHARGE PRESSURE Edward M. Gavin, Las Vegas,Nev., and Ralph E. Grey, Osborn, Leslie L. Aspelin, Elyria, and GeorgeF. Tate, Dayton, Ohio Application March 16, 1944, Serial No. 526,794

5 Claims. (01. 1583 6.4)

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) The invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto us of any royalty thereon.

This invention relates to fuel systems, and is particularly applicableto systems employing a plurality of fuel tanks, such, for instance,asthe fuel system on an aircraft.

An object of the invention is to provide a fuel system of this characterwith means to maintain the pressure in the fuel line at its entrance tothe carburetor or other fuel metering device substantially constant,while changing the connection which extends from the suction side of themain fuel pump from one tank to the next, as successive tanks areemptied.

More specifically, an object of the invention is to provide an emergencypump which becomes operative upon failure of the main pump to maintainthe desired discharge pressure, and remains operative until the mainpump has resumed substantially full discharge capacity.

Another object is to provide means to indicate when a shift from onemain tank to the next should be made.

Other objects and advantages will become evident from a consideration ofthe following description, taken in conjunction with the drawings,wherein,

The single figure of the drawing is a schematic assembly view of thevarious elements of a fuel system arranged and connected according tothe principles of our invention.

Like reference characters refer to like parts throughout the drawing.

Referring now to the drawing, an engine l carries a main fuel pump l2which is operatively connected to the engine to be rotated thereby, andadapted to maintain a given constant fuel pressure at the fuel inlet l3of the carburetor M. A gauge l 5 and a signal light I! are provided forindicating when the fuel is being maintained at the desired pressure. Asuction line It extends through a strainer If! to the common outlet ofthe tank selector cock 2!], the several inlets to the tank selector cockbeing respectively connected by supply pipes 22, 24 and 26 to the tanks28, 30 and 32. The supply pipes 22 and 24 stop at the bottoms of theirrespective tanks 28 and 30, but the supply pipe 26 is prolonged so as toextend upwardly into the tank 32 as at 34, so that a reserve quantity offuel 36 remains in the tank after the pipe 26 has drawn off fuel to thelevel of the upper end of the part 34. A short discharge line A-pressureresponsive switch 44 completes electrical connection between the battery42and. the motor 40 and signal light [1 whenever the-pressure at thecarburetor fuel inlet l3 fallsseveral pounds below the predeterminedpressure whichthe pumps l2 and 38 are set to maintain. Conduit means 46connects the carburetor fuel inlet I3 to the pressure operated part ofthe switch 44. A discharge line 48 connects the dischargeside of theemergency pump 38 into the short conduit 3! at the discharge side of theengine pump. A suction line 50 extends through a manually'operablereserve connector cock 52 into the bottom of the tank 32, whereby thesuction. side vofthe emergency pump 38 is connected to the-reserve fuelsupply 36. v

An air eliminator line 54 extends fromthe carburetor to the bottom of anair eliminator tank 56, which is partially filled with a liquid. A valve58 inthe line 54 permits it to be shutoff when that becomes desirable;Since both pumps l2 the damaged one, and for that reason, checkvalves 62and 60 are provided, both biased to prevent backward flow in the linesIt andii48,

respectively. The pressure responsive part-ofl the automatic switch 44may preferably be somade that the switch, in shutting off the motor 40,will respond to a pressure several poundslower than that at which therelief valve ofthe pump I2 is set. I

Assume that the engine. In is -stopped,,the pressure at the carburetorinlet l3 has dropped, and the tank selector cook 20 is turned to theposition which connects the tank 28, through the supply pipe 22 andsuction line IE to the suction side of the engine pump l2. If the manualswitch 43 is now closed, the emergency pump 38 will prime thecarburetor, the switch 44 shutting off the motor when the pressure isup. If the engine is not immediately started, the emergency pump Amanual switch 43 isprovided for dis-- connecting the battery from theelectric circuits.

The operation of the fuelsystem shown and described is substantially asfollows: 1 i

the discharge line 48 from flowing backwardly' through the pump 38 intothe tank.32.

When the tank 28 becomes empty, it will be a matter of several secondsonly until the engine pump [2 will be drawing some air through thesuction line l6 and discharging it into' the short conduit 31. When thisoccurs, the pressure-at the fuel inlet l3 will drop almost instantly,and the automatic switch 44 will beactuated thereby to connect thebattery 42,100 the motor 40 of the emergency pump 38, whereupon theemergency rmrnp38 will maintain the desired fuel pressure at thecarburetor fuel inlet l3,fthe air which had gotten into theshort'conduit 31 and into the carburetor, "being discharged through theair eliminator line-54. It is noted that the discharge line 48 of themotor driven pump 38 isalways full of fuelso that it needs only to beput under pressure to enable the pump 38 to take over when the pumpl2fails. v

The pump 38 is', ofcourse, designed for greater capacity than engineconsumption, and may thereforecycle from this cause at intervals ofseveral seconds. Thus the pressure at the fuel intakel3-wil1 reach thedesired value and the automatic switch u wnr stop the motor 48, then,as-fuelaisconsumed, the'pressure will drop at the inlet I ii a matter of7 several pounds, whereupon the switch will again start the motor 48 toopcrate the pump 38. i

This cycling may-be observed on the pressure gauge l5,andby thefiashingof' the signal light l"I",-whereupon thetank-selector cook 20should be turned to connect the tank 30 or any other full tank tothesuction side of the engine pump l2. Qrd-inariIy, in less-than half a;minute, the pump 12' picks up the prlmeand raises-the pressure at thefuel inlet 1 3 high enough to shut off the switch 44: andthusstop themotorpump '38.

If thesystem shown isbein used in combat aircraftg'it may happen that;the tank 32 is punctuned and the reserve: supply 36 lost, or the enginepump l2' maybe jammed ior otherwise incapacitated; I-In.such'a:case,the'reserve connector cock 52 i:maybe "turned sons to connect the motordriven pump 38, through the tank selector cook 28, to any tankwhichmaystill contain fuel.

Having shown and described a physical embodiment-of our invention, weclaim:

LfThe combination .inaan aircraftfuel system, of-a main'fuel-supplyreceptacle," a main fuel pump-having its xsuction side connected to saidmain fuel supply-receptacle, a discharge-pressure control means for saidmain fuel pump, a reserve fuel supply container, an auxiliary fuel pumphaving its suction. side connected to said reserve fuel supplycontainer, a; discharge-pressure controlmeansf'or saidauxiliaryfuelpump, a fuel receiving means,the discharge side of both said pumps beingconnected to said fuel receiving means, the discharge-pressure controlmeans of the auxiliary'fuel-pump being operable at the same pressure asthe main fuel pump for delivering fuel to said fuel receiving means, anda pros sureresponsive means'associated with the main fuel pump, adaptedupon a predetermined drop 4 in pressure at the discharge side of themain fuel pump to operate said auxiliary fuel pump.

2. The combination, in an aircraft fuel system, of a plurality of main"fuel supply receptacles, a main fuel pump, a discharge-pressure controlmeans for said main fuel pump, valve means for connecting the suctionside of said main fuel pump to any of said receptacles one at a time, areserve fuel supply container, an electric motor driven auxiliary fuelpump, a discharge-pressure controlmeans for said auxiliary fuel pump,means for connecting the suction side of said auxiliary fuel pump tosaid container, a fuel receiving means, means connecting the dischargeside of both said pumps to said fuel receiving means, thedischarge-pressure control means of the auxiliary fuel pump beingoperable at the same pressure as the main fuel pump for delivering fuelto said fuel receiving means, and an automatic electric switchresponsive to a predetermined drop in pressure at the fuel inlet openingof said fuel receiving means to 'close and'direct an electric current tooperate said'electric motor driven auxiliary fuel pump.

3. The combination, in an aircraft fuel system, of aplurality of mainfuel supply receptacles, a main fuel pump, means for selectivelyconnecting the suction side of said pump to any of said supplyreceptacles one at a time, a reserve fuel supply container, an auxiliaryfuel pump, means connecting the suction side of said auxiliary fuel pumpto said reserve fuel supply container, a fuel metering means, thedischarge side of both said pumps being connected to said fuel meteringmeans, valve means for disconnecting the suction side ofthe auxiliaryfuel pump from said reserve fuel supply container and connecting it intothe suction ;-line of the mainfuel pump, and a pressure-responsive meansassociated with the fuel metering means, adapted, upon a predetermineddrop inpressure at the fuel intake of said fuel metering means. tooperate said auxiliary fuel 4, The combination, in an aircraft fuelsystem, of aplurality of main fuelsupply receptacles, a main fuel pump,a selector Valve for connecting the suction inlet of said main fuel pumpto said main fuel supply receptacles one at a time, a reserve fuelsupply container, ,an auxiliary fuel pump, a reserve connector cock, afirst, a second and a third port in said connector cook, a firstpassageway connecting the first port to the reserve fuel supplycontainer, a second passageway connecting the second port to the suctionside of the auxiliary pump, a third passageway connecting the third portinto thesuction line of the main fuel pump, means in said reserveconnector cock operable to one. position to connect the first port tothe second, and to a second position toconnect,

thesecon-d port to the third, a check valvein the suction line of saidmain fuel pump between said main fuelpump and the point of. connectionof the third said passageway with the main pump suctionline, acarburetor, the discharge sides of bothsaid pumps being connected to thefuel inlet of said carburetor, and an automatic means re sponsive topressure drop at the fuel inlet of the carburetor to operate saidauxiliary fuel pump.

5. The combination, in an aircraft fuel system, of a plurality of mainfuel supply tanks, a main fuel pump, conduit means including a tankselector cock for selectively connecting the suction inlet of the mainfuel pump to the several tanks one at a time, a checkvalve in saidconduit meansbetweensaid selector .cock' and 1 said main vfuelpumnbiasedto-prevent fuelr flow from said pump back through said cook, areserve fuel supply container, an emergency fuel pump, conduitmeansincluding a two way cock for selectively connecting the suction inlet ofthe emergency fuel pump either to the reserve fuel supply container orto 5 the said main fuel pump conduit means at a point between said checkvalve and said tank selector cock, a carburetor, a conduit connectingthe discharge sides of both pumps to the fuel inlet of said carburetor,a check valve in said conduit biased 10 to prevent fiow from thedischarge side of the main fuel pump back through said emergency fuelpump, and an automatic means responsive to a pressure drop at the fuelinlet of the carburetor to operate said auxiliary fuel pump.

EDWARD M. GAVIN. RALPH E. GREY. LESLIE L. ASPELIN. GEORGE F. TATE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

